Tailscale service observer is a Go tool which watches Kubernetes services in a single namespace and updates the advertised routes of a Tailscale client over the client's HTTP API (tailscale web).
The observer expects to run in a context with a working Kubernetes configuration (either via kubeconfig file or in-cluster).
The environment variable TARGET_NAMESPACE must be set to the namespace(s) in which the observer should watch services.
You can specify multiple namespaces separated by commas.
The environment variable TAILSCALE_API_URL can be used to provide a custom URL for the Tailscale client's HTTP API.
By default, the observer expects the API to be reachable at http://localhost:8088.
The environment variable OBSERVER_ADDITIONAL_ROUTES can be used to advertise additional routes.
You can specify multiple routes separated by commas.
Entries which can be parsed as an IP address will be advertised as a <ip-address>/32 route.
Entries which can be parsed as a CIDR prefix will be advertised as that prefix route.
See the examples for Kubernetes manifests to get started.
To expose the in-cluster DNS server in your tailnet, you can advertise the in-cluster DNS IP address by adding it in the environment variable OBSERVER_ADDITIONAL_ROUTES.
Additionally, you can enable Tailscale's MagicDNS feature, and add the in-cluster DNS server as an additional resolver.
We recommend that you enable "Restrict to search domain", and set svc.cluster.local as the search domain.
This allows you to use the in-cluster service DNS names (<service>.<namespace>.svc.cluster.local) to access advertised services.